Core taker devices



United States Patent O 3,220,492 CORE TAKER DEVICES C P Lanmon II,Friendswood, Tex., assignor to Schlumberger Well Surveying Corporation,Houston, Tex., a corporation of Texas Filed Dec. 17, 1963, Ser. No.331,235 4 Claims. (Cl. 175-.4)

This invention relates to apparatus for obta-ining solid samples ofearth formations and, more particularly, pertains to a new and improvedcore-taking apparatus for obtaining a solid `sample of earth formationmaterial.

Generally, cores or samples of earth formation material are obtained bylowering a side wall sample taker assembly into the borehole to thelevel of the formation to be investigated. The sample taker assemblyincludes a gun body which receives a number of hollow core-takingbullets together with explosive means which are selectively operable sothat the bullets may be impelled towards and into a formation, with thehollow interior of the bullets thereby receiving the formation material.Usually, the core bullet is secured to the gun body by one or moreexible retrieving connections so that a pull, as by raising the gunbody, serves to withdraw the core bullet with a formation sample fromthe earth formations. Thus, a formation core sample can be retrieved tothe surface of the earth for examination and testing.

However, many problems are presented by the variety of formations whichare encountered in sampling operations. For example, the types offormations may be generally classified as (l) soft, (2) medium, (3)firm, (4) hard, and (5) extra hard. Thus, the problems may vary from thedifliculty in getting the bullet into the extra hard formations withoutdamage to the difficulty encountered in soft formations in thewithdrawal of the core bullet from the formation. To obtain core samplesfrom the various types of formations, different types of core bulletshave been designed to meet the various conditions arising. Aside fromthe problem of retrieving the core bullets, it is, of course, necessaryto obtain a core sample which is representative of the formation tested.

Particularly in the soft to firm formations, recovery of core bulletshas been facilitated by providing the core bullet with a separableforward portion in the form of an annular cutting ring which generallyhas a slightly greater outer diameter than the core barrel. Thus, thering forms an enlarged hole relative to the body of the bullet toalleviate sticking of the bullet body in the formation. When a pull isexerted on the body of the bullet, ,it should separate from the cuttingring thereby to leave the cutting ring in the formation. Various cuttingring attachments have heretofore been used such as the types disclosedin Patents No. 2,923,530, No. 3,101,- 79.7 or No. 3,072,202.

It has been found in many instances that the core bullet becomes sofirmly embedded that in pulling on the bullet in the formations, thewire-retrieving connect-ions are broken.

Accordingly, it is an obiect of the present invention to provide new andimproved core-taking apparatus for minimizing the retrieval pullrequired on a core-taking bullet.

Another object of the present -invention is to provide new and improvedcore-taking apparatus which is selfretracting from earth formations.

Still another object of the present invention is to provide new andimproved core-taking apparatus which is hydraulically self-retractingfrom earth formations.

In apparatus for obtaining a core sample, in accordance with the presentinvention, a gun body receives one or more core-sampling bullets whichmay be disposed ICC lengthwise of the gun body. The bullet is adapted tobe impelled toward and into earth formations by explosive means and hasa body member with a cutting ring member releasably received on itsforward end. Means are provided to operate after the bullet has left agun body and is in the earth formations to move the body memberrearwardly relative to the ring member. Thus, the body member isretractable from earth formations relative to the ring memberindependent of the usual retrieving wire members.

The novel features of the present invention are set forth withparticularity in the appended claims. The present invention, both as toits organization and manner of opera- `ion together with further objectsand advantages thereof, may best be understood by way of illustrationand example of certain embodiments when taken in conjunction with theaccompanying drawings in which:

FG. l is a View in partial cross-section of apparatus embodying thepresent invention for obtaining a core sample and illustrated in a wellbore;

FIG. 2 is a view in cross-section of a bullet embodying the presentinvention; and

FIG. 3 is a view in cross-section of a bullet embodying another form ofthe present invention.

In FIG. 1 of the drawings, there is shown a gun block or body 10disposed in a borehole 11 opposite a formation 12 of interest. Usually,borehole 11 contains a drilling mud 13.

Gun block 10 has a cylindrical bore 14 adjoining a bore 15 of smallerdiameter, the bore 15 forming a powder chamber which terminates short ofthe rear surface 16 of the gun block. Chamber 15 contains an appropriateand conventional explosive propellant 1'7 while bore 14 receives algenerally cylindrical core-taking device or bullet assembly 18constructed inaccordance with the present invention. Although notillustrated, gun block 10 generally contains additional bulletassemblies in respective bores distributed along a vertical axis for thegun block.

Bullet assembly or bullet 18, near its rearward end, has an annulargroove which receives an O-ring 19 to provide a fluid-tight seal for thebullet assembly 18 in the bore 14, and flexible retrieving wires 20 aresecured in a conventional manner between the bullet assembly and gunblock 10 to permit the bullet body of the assembly to be retrieved. Aconventional igniter 21 suitably mounted in the block 10 may be employedto detonate the explosive propellant 17 and thereby propel the bullet 18toward and into the formation.

Referring now to FIG. 2, bullet or bullet body member 18 includes acentral tubular sample-receiving core part 21, with an attached rearwardbottom part 22. Forward part 21 has a fowardly facing shoulder 24 andreleasably receives a cutting ring or release Inernber 25. A snap ring26 is provided to insure retention of ring 25 Yon part 21. Ring member25 has the usual, conically shape-d forward surface and is disposedslightly rearwardly of the forward cutting edge 27 on the tubular part21. Ring member 25 is also slightly greater in overall diameter than thediameter of the body portion rearwardly of the cutting ring member toreduce the area of the bullet in the formation subject to hydrostaticpressure. The purpose of the cutting ring member 25 is to provide anoversized hole so that the outer body of the bullet 18 is prevented fromintimate contact with the earth formations, the ring member 25 beingleft embedded in the earth formations. Of course, the precise connectionand -arranegment of the ring member relative to the bullet body isimmaterial to the present invention so long as the ring member when inthe earth formations is releasable from the bullet body. Theabovedescribed ring arrangement, however, is preferable since theforward end of part 21 extends beyond ring 25 and obtains a better coresample more reliably.

Tubular core part 21 also has ports 28 in its side walls and connections29 (FIG. 1) for attachment of retrieving wire elements 20 to the bulletbody.

Bottom part 22 provides a bottom 30 for the tubular core part 21 and hasan O-ring seal 31. Bottom part 22 also has stepped anged portions 32,33. Flanged portion 32 forms a piston which is slidably and sealinglyreceived in gun bore 14 by means of the O-ring 19. An inner,self-releasing sleeve 35 abuts the shoulder formed on flange portion 33and an outer actuating sleeve 36 abuts the shoulder formed on angedportion 33. Inner sleeve 35 terminates at forward shoulder 24 whileouter sleeve 36 abuts ring member 25 and spaces the ring member a shortdistance above shoulder 24. Access ports 37, 38 are provided toaccommodate connections 20 and ports 28 where necessary.

Intermediate of flanged portion 33 and forward shoulder 24 a portion ofthe part 21 is reduced in diameter at 39 to slidably and sealinglyreceive a piston portion 40 of the self-releasing sleeve 35. Pistonportion 40 has internal and external grooves receiving the O-rings 41,42 so as to seal relative to part 21 and outer sleeve 36. An O-ring 43is proveded on part 21 above the recessed portion 39 to seal the part 21relative to sleeve 3S. A chamber 44 is formed between sleeve 35 andparts 21 and is pressure sealed by the O-rings 41, 43. Sleeve 35 has anend surface 45 which is adjacent but not in contact with the cuttingring member 25. Flanged portion 33 also has an O-ring 46 providing aseal between portion 33 and outer sleeve 36. Sleeve 36 has an internalannular recess at 47 weaking the structure of the sleeve. The lower endof piston portion 40 is recessed at 48 and adapted for fluid connectionto recess 47, as by a passage 48a.

In operation, when the powder 17 is ignited, the bullet is acceleratedfrom bore 14 toward and into adjacent earth formations. Snap ring 26 isdisplaced from its groove leaving the cutting ring 25 free, the cuttingring staying on the bullet body due to the forward movement of thebullet body. As the forward end of the bullet penetrates the formation,the cutting ring makes a large hole and keeps the portion of the bulletand sleeve 36 rearwardly of the ring from intimate contact with theformation. When ring member 25 impacts with the earth formati-ons,weakened section 47 of outer sleeve 36 fails and lets hydrostaticpressure into chamber 48. Chambers 48 and 44, it will be recalled, hadpreviously been sealed from the hydrostatic pressure by seals 42, 46,41, 43, 31. There will be a force produced by the hydrostatic pressureto slide self-releasing sleeve 35 axially along part 21 into engagementwith ring 25. This force is equal to the area bounded by the seals 43,41 times the hydrostatic pressure. The self-releasing sleeve 35 willthen press against the ring 25 and part 21 will be driven out of theformation by an equal and opposite force for retrieval by the fasteners20, (FIG. 1).

FIGURE 3 shows another bullet assembly that will perform the samefunction as the bullet shown in FIGURE 2. The principal difference is inthe valve means to allow the hydrostatic pressure to act on anunbalanced area after the bullet has struck the formation. Connections29 and access ports are not shown for clarity of illustration.

As shown in FIG. 3, an outer sleeve 50 is provided and together withseals 43a, 41a,` 46a, 31 and parts 21, 22 form sealed-off chambers 44and 48. A rod member 51 extends longitudinally bewteen ring member 25and a break valve 52 in sleeve 50. Break valve 52 is adapted to besheared open upon the application of sufficient force via rod member 51to place the chamber 4S in fluid communication with hydrostatic wellpressure exterior of the bullet.

In operation, the bullet strikes the formation and the decelerationinertia causes the rod member 51 to press against the break valve 52 andrupture it. When break valve 52 is ruptured, hydrostatic pressure isallowed into chamber 48. Chambers 48 and 44 have previously been sealedfrom outside pressure by the various seals. When hydrostatic pressure ispermitted in chamber 48, there is a force applied to slide sleeve 50 inrelation to part 21. This force is equal to the area bouned by seals43a, 41a times the hydrostatic pressure. In this manner ring member 2Sis left in the formation as part 21 is withdrawn. The assembly isretreived by the fasteners attached to the gun, (FIG. 1).

While particular embodiments of the present invention have been shownand described, it is apparent that changes and modifications may be madewithout depatring from this invention in its broader aspects and,therefore, the aim in the appended claims is to cover all such changesand modifications as fall within the true spirit and scope of thisinvention.

What is claimed is:

1. A formation core-taking device adapted to be fired from a gun bodyinto earth formations about a well bore comprising: a tubularcore-taking body member having a forward end, a formation-cutting ringmember releasably received on said forward end, means operativelycoupled between said body member and said ring member and responsive tohydrostatic pressures after ejection from a gun body for providing aforce on said ring member, and means for admitting hydrostatic pressuresto said hydrostatic pressure-responsive means in response to impact ofsaid core-taking device with earth formations to urge said body memberand said ring member in opposite directions relative to one another whensaid ring member and forward end of said body member are embedded inearth formations.

2. A formation core-taking device adapted to be fired from a gun bodyinto earth formations about a well bore comprising: a tubularcore-taking body member having forward and rearward ends and areduced-diameter intermediate portion; a formation-cutting ring memberreleasably received on said forward end; means responsive to hydrostaticpressure for releasing said ring member including a slidable sleevemember around said body member and adapted for forward travel to releasesaid ring member and means fiuidly sealing said sleeve member to saidbody member for providing sealed forward and rearward annular chambersaround said intermediate body portion between said body ends; and meansresponsive to impact with earth formations for admitting hydrostaticpressure into said rearward chamber to urge said sleeve member forwardlyand said body member rearwardly when said forward body end is embeddedin earth formations.

3. A formation core-taking device adapted to be fired from a gun bodyinto earth formations about a well bore comprising: a tubularcore-taking body member having forward and rearward ends and areduced-diameter intermediate portion; a formation-cutting ring memberreleasably received on said forward end; means responsive to hydrostaticpressure for releasing said ring member including a slidable firstsleeve member around said body member .and adapted for forward travel torelease said ring member and means fiuidly sealing said first sleevemember to said body member at longitudinally spaced intervals forproviding sealed forward and rearward annular chambers around saidintermediate body portion between said body ends; passage means foradmitting hydrostatic pressure into said rearward chamber; and meansnormally sealing said passage means and responsive to impact with earthformations for admitting hydrostatic pressure into said passage means,said impact-responsive means including a second sleeve member coveringsaid passage means and having a weakened portion adapted to fail under apredetermined force and a forward portion for transmitting impact forcesto fail said weakened p0rtion and admit hydrostatic pressure into saidrearward chamber to urge -said rst sleeve member forwardly and said bodymember rearwardly when said forward body end is embedded in earthformations.

4. A formation core-taking device adapted to be tired from a gun bodyinto earth formations about a well bore comprising: a tubularcore-taking body member having forward and rearward ends and areduced-diameter intermediate portion; a formation-cutting ring memberreleasably received on said forward end; means responsive to hydrostaticpressure for releasing said ring member including a slidable sleevemember around said body member and adapted for forward travel to releasesaid ring member and means fluidly sealing said sleeve member to saidbody member at longitudinally spa-ced intervals for providing sealedforward `and rearward annular chambers around said intermediate bodyportion between said body ends; passage means for admitting hydrostaticpressure into said rearward chamber; and means normally sealing saidpossage means and responsive to impact with earth formations foradmitting hydrostatic pressure into said passage means, saidimpact-responsive means including a closure member sealing said passagemeans, said closure mem-ber having a weakened portion adapted to failunder a predetermined force, and means engaged with said weakenedportion for transmitting impact forces thereto to fail said weakenedportion and admit hydrostatic pressure into said rearward chamber tourge said sleeve member forwardly and said body member rearwardly whensaid forward body end is enbedded in earth formations.

References Cited by the Examiner UNITED STATES PATENTS 2,901,220 8/1959Linn 175-4 X 2,923,530 2/1960 Fields 175-4 X 3,072,202 1/1963 Brieger175-4 3,101,797 8/1963 Brieger 175-4 CHARLES E. OCONNELL, PrimaryExaminer.

1. A FORMATION CORE-TAKING DEVICE ADAPTED TO BE FIRED FROM A GUN BODYINTO EARTH FORMATION ABOUT A WELL BORE COMPRISING: A TUBULAR CORE-TAKINGBODY MEMBER HAVING A FORWARD END, A FORMATION-CUTTING RING MEMBERRELEASABLY RECEIVED ON SAID FORWARD END, MEANS OPERATIVELY COUPLEDBETWEEN SAID BODY MEMBER AND SAID RING MEMBER AND RESPONSIVE TOHYDROSTATIC FROM A GUN BODY FOR PROVIDING A FORCE ON SAID RING MEMBER,AND MEANS FOR ADMITTING HYDROSTATIC PRESSURES TO SAID HYDROSTATICPRESSURE-RESPONSIVE MEANS IN RESPONSE IN IMPACT CORE-TAKING DEVICE WITHEARTH FORMATION